Evaluation of effective conductivity of copper post and transmission losses of post-wall waveguide in millimeter wave band

This paper presents a measurement method for determining the effective conductivity σ
_p
of copper posts in a copper-clad dielectric substrate in the millimeter-wave region. The conductivity is indirectly evaluated from measured resonant frequencies and unloaded Q values of a number of Whispering Gallery modes excited in a post-wall circular resonator with a large diameter of 10 - 30 wavelengths. We measure σ
_p
in 40 - 51 GHz band. The measured σ
_p
of the copper post decreases with the increase in the frequency. We confirm the measured results by comparing between the calculated results and the measured results of transmission losses for post-wall waveguides.